TL;DR: Even as an orchestral composer, I am having absolutely no trouble with the MacBook in Logic Pro X or Finale v. 25. Both use at most a bit over half of the MacBook's dual core. If you're throwing together orchestral demos or composing from scratch, the MacBook will be a pleasure to use. It's zippy, sharp, and ridiculously light. AND THE SPEAKERS ARE KILLER.

An early 2015 12 inch MacBook with 1.1 Ghz processor (if connected to a large monitor) works better with Finale for me than a late 2012 MacMini with 2.5 Ghz processor. I don't use Logic Pro or any kind of DAW, though, and make only minor use of playback (and then only with Finale's inbuilt sounds), and I use QWERTY and Trackpad for music entry. On the other hand, I am working with some fairly large full scores.

It's worth pointing out that Finale 25 has made considerable improvements in CPU (and therefore battery) efficiency over previous versions.However, the "bug" still exists where the playback thread uses 100% of one core on any CPU, no matter what its performance.